1. Field of the Invention
The present invention relates to a collision avoidance system for aircraft including transponders such as ATC, SIF, IFF or DABS transponders. More particularly, the present invention relates to a collision avoidance system for aircraft, incorporating transponders, to provide proximity warning indications to a pilot in the absence of altitude information from other aircraft, normally used as a collision avoidance indication, and indicating to the pilot a direction for evasive flight to avoid collision. The proximity warning indication may comprise one or a combination of (a) distance between one's and an other aircraft, (b) approaching speed, and (c) time to collision.
2. Description of Prior Art
In a conventional system for collision avoidance of aircraft, when altitude information of an other aircraft is not obtained, instructions to a pilot are not available as to direction of flight for collision avoidance. In the conventional system, the pilot is frustrated by the failure to receive such information and cannot take evasive action until such information is obtained.